Mantle dynamics beneath the Gibraltar Arc (western Mediterranean) from shear-wave splitting measurements on a dense seismic array

Controversial evolutionary models have been proposed for the Gibraltar Arc system, a complex interaction zone between the Eurasia and African plates. Here we derive new mantle anisotropic constraints from SKS splitting measurements on a dense network of about 90 broad-band stations deployed over South Iberia and North Morocco. The inferred fast polarization directions (FPD) clearly show a spectacular rotation along the arc following the curvature of the Rif-Betic chain, while stations located at the South and South-East edges show distinct patterns. These results support geodynamical processes invoking a fast retreating slab rather than convective-removal and delamination models. The FPD variations along the Gibraltar arc can be explained by fossil anisotropy acquired during the Western Mediterranean Eocene subduction, while changes to the South and South-East of the Rif-Betic chain could be the imprint of a flow episode around an Alboran high velocity slab during its Miocene fragmentation from the Algerian slab. Citation: Diaz, J., J. Gallart, A. Villasenor, F. Mancilla, A. Pazos, D. Cordoba, J. A. Pulgar, P. Ibarra, and M. Harnafi (2010), Mantle dynamics beneath the Gibraltar Arc (western Mediterranean) from shear-wave splitting measurements on a dense seismic array, Geophys. Res. Lett., 37, L18304, doi:10.1029/2010GL044201.